103: StageFlexer ® Tech Report - Flexcell International Corp.

Tech Report 103:
StageFlexer®
Quantification of strain at the membrane level
Authors: Colin Frazier, B.S., David Anderson, B.S., Michelle E. Wall, Ph.D., Ruwan Sumanasinghe,
Ph.D., and Albert J. Banes, Ph.D.
Document: StageFlexer Tech Report, Rev 2.4
01-09-15
Culturing Cells in a Mechanically Active Environment™
Flexcell International Corporation  2730 Tucker Street, Suite 200  Burlington, NC 27215
800-728-3714  (919) 732-1591  FAX: (919) 732-5196  www.flexcellint.com
COPYRIGHT © 2009 FLEXCELL INTERNATIONAL CORPORATION
FLEXCELL® INTERNATIONAL CORPORATION
INTRODUCTION
StageFlexer® body with the top surface of
the Loading Station™ just below the
StageFlexer® membrane surface. When
vacuum is applied to the StageFlexer®, the
membrane is pulled over the Loading
Station™ creating a single-plane, uniformly
stretched circle (Fig. 2). A silicone-based
lubricant is used to lubricate the Loading
Station™, forming an effective grease
boundary layer to minimize friction between
the silicone membrane and the acrylic
Loading Station™. Given that the part of the
membrane stretching over the Loading
Station™ (circular loading post) has an
infinite number of radii, each cell plated in
this area will receive the same strain in the
direction of the radius passing through its
center.
The StageFlexer® is designed to allow the
user to view cell stretching activity under a
microscope (Fig. 1). The cell growth area is
part of a treated 42 mm diameter silicone
membrane. The membrane is clamped and
sealed above a small cylindrical vacuum
chamber into which the membrane is pulled
to apply strain to the cells growing on the
silicone surface. The membrane can be
deformed freely in an open chamber or over
a Loading Station™ to apply uniform biaxial
strain to the cells. The Loading Station™
comes in three different diameters (25 mm,
28 mm, and 31 mm) for varied growth
surface area. The StageFlexer® can be run
with the Flexcell® Tension System to stretch
the cells under specific regimens while they
are being viewed under a microscope.
Figure 2. Schematic of strain application
in a StageFlexer®.
Figure 1. A StageFlexer® microscopy
strain device.
STRAIN QUANTIFICATION
STAGEFLEXER® LOADING STATIONS™
The three different diameters of Loading
Stations™ were each placed into the
StageFlexer® for testing. The strain was
experimentally determined by imprinting the
StageFlexer® membrane with a biaxial
pattern. Strain was determined by labeling
the distance between each pair of dots and
measuring their change relative to vacuum
levels. All vacuum measurements were
made using a digital manometer. Vacuum
The StageFlexer® Loading Station™ is
designed to provide uniform radial and
circumferential strain across the membrane
surface along all radii. The uniformity
remains along the length of all radii that
remain in contact with the top surface of the
post during stretching. The Loading
Station™ is composed of acrylic plastic. The
design centers it within the well of the
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FLEXCELL® INTERNATIONAL CORPORATION
was applied with a Robinair vacuum pump
(model #15101-B). Loctite® lubricant was
applied to each Delrin® Loading Station™ to
enable frictionless movememt against the
rubber membrane. Designated distances
were measured using the following method:
% Substrate Elongation
16.0
12.0
8.0
4.0
0.0
A Canon Compact EOS Digital Rebel XTI®
camera equipped with a macro lense was
leveled and fixed directly above the
membrane. The resolution of the image was
adjusted to ensure each pair of dots filled the
maximum horizontal distance across the
digital image, maximizing the number of
pixels and measurement accuracy. A FX5000™ Tension System regimen was
designed to step through pressures from 090 kPa. At each static step, the image was
captured using a Lexar™ memory card.
Adobe Photoshop® CS2 image analysis
software was used to measure the distances
between the dots.
0
20
40
60
80
100
Vacuum level (-kPa)
Figure 3. Average radial strain vs.
vacuum level for a StageFlexer® membrane
atop a 25 mm BioFlex® Loading Station™.
% Substrate Elongation
16.0
12.0
8.0
4.0
0.0
0
20
40
60
80
100
Vacuum Level (-kPa)
Figure 4. Average radial strain vs.
vacuum level for a StageFlexer® membrane
atop a 28 mm BioFlex ® Loading Station™.
RESULTS AND DISCUSSION
The results showed a nearly linear
relationship between vacuum level and
strain (Figs. 3-5). Given that two different
radii of dots had uniform radial strain, the
assumption was made that each radius was
increasing uniformly with vacuum level.
With this, the change in circumference could
be measured from a single point; i.e., the
same dots used for radial strain.
% Substrate Elongation
10.0
8.0
6.0
4.0
2.0
0.0
0
20
40
60
80
100
Vacuum Level (-kPa)
The following three figures show the
experimental results for the vacuum level vs.
strain relationship for each Loading
Station™ diameter (25 mm, 28 mm, and 31
mm).
Figure 5. Average radial strain vs.
vacuum level for a StageFlexer® membrane
atop a 31 mm BioFlex® Loading Station™.
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